17w18b crash when 1.6.4 FML server is on list

when i have 1.6.4 FML server on list launching 17w18b client crash
server is old 1.6.4 FML with Pixelmon mod 3.0.2 ip : pixel-mon.pl

LOG from server :
server version :

2017-05-07 14:15:21 [INFO] This server is running Cauldron-MCPC-Plus version git-Cauldron-MCPC-Plus1.6.4-1.965.21.144 (MC: 1.6.4) (Implementing API version 1.6.4-R2.1-SNAPSHOT)

2017-05-07 14:21:49 [INFO] Disconnecting /xxx.xx.xx.xx:44520: Protocol error
2017-05-07 14:21:49 [INFO] /xxx.xx.xx.xx:44520 lost connection

LOG from client :

14:15:09 launcher main info Preparing to launch minecraft client for 17w18b
14:15:09 launcher main info Checking installations.
14:15:09 launcher main info Minecraft client 17w18b is ready to start.
14:15:09 launcher main info Starting!
14:15:10 launcher main info Using default game log configuration client-1.12.xml (outputs XML)
14:15:11 bhm Client thread info Setting user: minecraft7net
14:15:13 bho Client thread warn Skipping bad option: lastServer:
14:15:13 bho Client thread warn Skipping bad option: streamPreferredServer:
14:15:13 bhm Client thread info LWJGL Version: 2.9.4
14:15:13 cei Client thread info Reloading ResourceManager: Default
14:15:14 cgu Client thread warn Missing sound for event: minecraft:entity.player.hurt_drown
14:15:14 cgu Client thread warn Missing sound for event: minecraft:entity.player.hurt_on_fire
14:15:14 cgu Sound Library Loader info Starting up SoundSystem...
14:15:15 cgu Thread-3 info Initializing LWJGL OpenAL
14:15:15 cgu Thread-3 info (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
14:15:15 cgu Thread-3 info OpenAL initialized.
14:15:15 cgu Sound Library Loader info Sound engine started
14:15:21 cdc Client thread info Created: 1024x512 textures-atlas
14:15:23 nc Client thread info [STDOUT]: Narrator library for x64 successfully loaded
14:15:28 brt Client thread error Can't ping pixel-mon.pl: Internal Exception: java.io.IOException: Istniejące połączenie zostało gwałtownie zamknięte przez zdalnego hosta
14:15:29 bhm Client thread fatal Reported exception thrown!
f: Ticking screen
at bhm.t(SourceFile:1606)
at bhm.ax(SourceFile:964)
at bhm.a(SourceFile:404)
at net.minecraft.client.main.Main.main(SourceFile:123)
Caused by: java.lang.NullPointerException
at io.netty.bootstrap.Bootstrap.checkAddress(Bootstrap.java:358)
at io.netty.bootstrap.Bootstrap.doResolveAndConnect(Bootstrap.java:180)
at io.netty.bootstrap.Bootstrap.connect(Bootstrap.java:162)
at io.netty.bootstrap.Bootstrap.connect(Bootstrap.java:143)
at brt.b(SourceFile:241)
at brt.a(SourceFile:45)
at brt$1.a(SourceFile:144)
at go.l(SourceFile:382)
at brt.a(SourceFile:254)
at bmq.e(SourceFile:115)
at bhm.t(SourceFile:1596)
... 3 more